Static seals currently available which operate over a wide range of flange deflection are of two categories. These categories are the "E-seal" category, and the inflatable seal category.
The E-seals are only short bellows. Most of their squeezing force comes from compressing them as springs. The remainder of the squeezing force comes from the pressure of the sealed fluid, acting upon the end corrugations of the bellows. The total squeezing force is not large, since a bellows is basically a flexible container, rather than a seal. Another limitation of E-seals is that they must generally be circular in the plane view, since E-seals are not so easily formed into other shapes, either in a plane or out of a plane.
The inflatable seals are hoses filled with air under pressure. Before they are pressurized, these hoses have oval cross-sections. Under pressure, the hoses try to become circular in cross-section, and in the process, they push against the vessel flanges to provide the squeezing force needed for sealing. Inflatable seals require a reliable air supply system, including a tank or compressor to supply the air, as well as means for regulating the hose pressure.
Inflatable seals are typically made of low strength materials, such as rubber, or rubber-like materials, so they are only suitable for the lower working pressure applications. (They are sometimes used to maintain cabin pressure in aircraft). Because of their material, they cannot be used at high temperatures. They become somewhat brittle at very low temperatures. E-seals, which are typically metallic, are suitable for high working-pressures, high temperatures, and low temperatures. However, the E-seals generally cannot accommodate as wide a range of flange deflection as can the inflatable seal. For the very high working pressures, "C-ring" seals, "O-ring" seals, and many other types of seal can be used. Unfortunately seals which are good for the very high working pressures are not so acceptable for applications where there is a wide range of deflection of the vessel flanges.
There are a wide variety of static seals available, each type being the best currently available choice for one challenge or another. Because of these many different challenges, there will always be a need for improved static seal designs.
It is a primary object of the present invention to provide seals for applications where there is a wide range of deflection of the vessel flanges, and where the squeezing force (or force for sealing) is much larger than can be obtained from other seals with large deflection capability.
Another object of the present invention is to provide low pressure seals with a capability for good sealing over wide ranges of flange deflection, combined with the capability to provide a squeezing force comparable to the inflatable seals, but which does not require any provisions for its own air supply.
Yet another object of the present invention is to provide a good low pressure seal, (metallic or of other material) with a wide range of deflection, which is not necessarily circular in its plan view, but which can be readily formed, because it has a cross-section of simple geometry which does not have deep corrugations, into any general shape either in or out of a plane.
It is a general object of this invention to improve static seal technology.